1. Field of the Invention
The present invention relates in general to connectors used in a fluid circuit for an automotive air cooling system, and more particularly to connectors of a type which is mounted to a header (viz., refrigerant collection tank) of a heat exchanger to provide a fluid communication between the header and a fluid pipe connected to the connector.
2. Description of the Prior Art
In order to clarify the task of the present invention, one conventional connector of the above-mentioned type will be described with respect to FIGS. 5 and 6 of the accompanying drawings.
In FIG. 5, there is shown a heat exchanger 1 to which two conventional connectors 7 and 8 are practically applied.
The heat exchanger 1 shown is a condenser installed in a fluid circuit of an automotive air cooling system. That is, the condenser is a device for changing high pressure refrigerant gas to a liquid by emitting heat from the hot refrigerant to the cooler atmosphere.
As shown in FIG. 5, the heat exchanger 1 comprises generally inlet and outlet headers (or refrigerant collection tanks) 2 and 3 which are laterally spaced. These headers 2 and 3 are each constructed of an aluminum alloy or the like. Between these headers 2 and 3, there extend a plurality of rectangular-section refrigerant flow tubes 4 and a plurality of corrugated heat radiation fins 5 which are alternatively arranged. The tubes 4 and fins 5 are each constructed of an aluminum alloy or the like. The tubes 4 and fins 5 thus constitute a core portion 6 of the heat exchanger 1. Each header 2 or 3 is a cylindrical hollow member having upper and lower ends hermetically closed. Each tube 4 has both open ends exposed to the interior of the headers 2 and 3. For this exposure, each header 2 or 3 has at an inner side thereof a plurality of rectangular openings into which the open ends of the tubes 4 are received. Brazing is used for hermetically and securely connecting the parts of the heat exchanger 1. A bracket 9 is fixed to an upper portion of the outlet header 3, which is used for mounting the heat exchanger 1 to a vehicle body. When needed, a similar bracket is fixed to the inlet header 2 for the same purpose.
An inlet connector 7 is mounted to an upper portion of the inlet header 2 and an outlet connector 8 is mounted to a lower portion of the outlet header 3. To the inlet connector 7, there is connected a pipe 13a which extends from a compressor (not shown) of the fluid circuit of the air cooling system, and to the outlet connector 8, there is connected a pipe 13b which extends to an expansion valve (not shown) of the fluid circuit. Accordingly, under operation of the air cooling system, high pressure high temperature refrigerant gas from the compressor is led into the heat exchanger 1 through the inlet connector 7, and condensed liquid refrigerant thus collected in a lower portion of the outlet header 3 is led to the expansion valve through though the outlet connector 8.
FIG. 6 shows in detail a manner in which the outlet connector 8 is mounted to the outlet header 3. It is to be noted that the inlet connector 7 is mounted to the inlet header 2 in substantially the same manner as in the outlet connector 8.
As is seen from FIG. 6, the outlet connector 8, which is constructed of an aluminum alloy, is of a generally rectangular-parallelepiped block including six surfaces, which are a header mating surface 10, a pipe connecting surface 11, a pair of side surfaces 12a and 12b, an upper surface 12c and a lower surface 12d. The mating surface 10 is concave to intimately mate with a cylindrical outer surface of the outlet header 3. The outlet connector 8 is secured to the lower portion of the outlet header 3 through a brazing "C" applied entirely to the mating portions of the connector 8 and the header 3. The outlet connector 8 is formed with both a through bore 14 which extends between the mating and connecting surfaces 10 and 11, and a threaded bore 15 which is exposed to the connecting surface 11. Although not shown in the drawing, the through bore 14 is exposed to the interior of the outlet header 3 through an opening formed in the cylindrical wall of the outlet header 3. When the heat exchanger 1 is installed in the fluid circuit of the air cooling system, a leading end of the pipe 13b is intimately and hermetically thrust into the through bore 14 through a seal member (not shown). For tight connection between the pipe 13b and the outlet connector 8, a bolt 50 held by a flange 52 of the pipe 18b is engaged with the threaded bore 15.
As has been mentioned hereinabove, brazing is employed for assembling the heat exchanger 1. More specifically, before carrying out the brazing, the parts of the heat exchanger 1 are provisionally assembled with usage of suitable tools in such a manner that neighboring parts contact at their mating portions. One of the mating portions has a brazing sheet (clad) previously applied thereto. The brazing sheet is made of an aluminum alloy including a larger amount of silicon. Furthermore, before the brazing, the inlet and outlet connectors 7 and 8 are provisionally or incompletely fixed to the respective headers 2 and 3 through argon arc spot welding. The parts thus provisionally assembled are then put into a furnace of a certain atmosphere for a given time to achieve brazing. With this, the heat exchanger 1 is tightly assembled.
However, hitherto, it is very difficult to produce or assemble a heat exchanger 1 which is free of ill-brazing. In fact, if such ill-brazing occurs, the heat exchanger 1 produced tends to suffer from undesired leakage of refrigerant from the ill-brazed portion when practically operated in the fluid circuit of the air cooling system. Accordingly, in these days, when produced, all of the heat exchangers 1 are subjected to a leakage test using a compressed air.
In the leakage test, one of the through ports 14 of the inlet and outlet connectors 7 and 8 is closed by a plug, and a compressed air is led into the heat exchanger 1 through the other through port 14, and the pressure in the heat exchanger 1 is monitored for a given time. If a certain reduction of the pressure is found, it is judged that the heat exchanger 1 has at least one ill-brazed portion to cause such air leakage.
However, due to inherent construction of the inlet and outlet connectors 7 and 8, the heat exchanger 1 has the following drawbacks.
First, it is difficult to effectively use the argon arc spot welding for provisionally fixing the inlet and outlet connectors 7 and 8 to the respective headers 2 and 3. In fact, the work for arc-welding the connectors 7 and 8 to the headers 2 and 3 needs a lot of time for its difficulty. This is because of a marked difference in thermal capacity between the connector 7 or 8 and the header 2 or 3. As is easily understood from FIG. 6, due to the solid and bulky structure, each connector 8 or 7 has a great thermal capacity as compared with a portion of the header 3 or 2 to which the connector 8 or 7 is welded. Considering that a desired argon arc spot welding is obtained only when the welding is applied to parts which have been heated up to the same level, such great difference in thermal capacity makes the argon arc spot welding to such parts 8 and 3 (or 7 and 2) very difficult.
Second, the leakage test is troublesome and time consuming. In fact, before feeding a compressed air into the heat exchanger 1 for the test, the following steps are needed. First, a plug is fitted to one through bore 14 of the connector 7 or 8 and a bolt held by the plug is engaged with the threaded bore 15 of the connector 7 or 8. Then, an air feeding tube extending from an air compressor is fitted to the other through bore 14 of the other connector 8 or 7 and a bolt held by the tube is engaged with the threaded bore 15 of the other connector 8 or 7. Once the leakage test is finished, the plug and the air feeding tube are removed from the respective connectors 7 and 8 by carrying out a reversed manual work. These steps are troublesome and time consuming.